This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Genomic integrity is essential for the well-being and survival of organisms. Cells spend tremendous energy to protect the information held within the DNA. DNA replication is highly regulated and coordinated to ensure that the entire genome is replicated once and only once per cell division cycle. Further, various DNA lesions are recognized and processed by different DNA repair pathways. The goal of this work is to use small-angle X-ray scattering to address several long-standing questions about protein complexes that function in the nucleotide excision repair pathway and nucleoprotein assemblies that are formed during the initiation phase of bacterial DNA replication. We will obtain information on the size, shape, and molecular weight of these complexes. The information will be used to formulate models of how they function in vivo. Understanding the structure and function of these assemblies is important as the maintenance of genetic information is a fundamental process shared by all kingdoms of life, and will impact how we view DNA replication and repair, cell proliferation, and other biological processes such as senescence and tumorigenesis.